New Post: _rasterizer.Open(ms) throws System.NullReferenceException in .net 4.5

What version of native Ghostscript library do you have installed? If you have older version there is a chance that 'gsapi_set_arg_encoding' is not exposed. Current release is 9.14 which you can download and install from http://www.ghostscript.com/download/gsdnld.html

Cheers,
Josip